Unitized oil rings



Dec. 5, 1967 P. E. HARRIS 3,356,375

UNITI ZED OIL RINGS Filed Dec. i. 1964 2 Sheets-Sheet 1 ATTORNEYS Dec.5, 1967 P. E. HARRIS 3,356,375

UNITIZED OIL RINGS Filed Dec. 4, 1964 2 Sheets-Sheet 2 INVENTOR. PAUL E.HARRIS ATTORNEYS United States Patent 3,356,375 UNITIZED OIL RINGS PaulE. Harris, 400 S. Plum St., Hagerstown, Ind. v 47346 Filed Dec. 4, 1964,Ser. No. 419,267 13 Claims. (Cl. 277--9.5)

ABSTRACT 0F THE DISCLOSURE A unitized oil ring is provided in which thespacerexpander is adhesively bonded to the side rails in a precompressedcondition. The adhesive utilized is chosen so that it has suflicientshear strength at room temperatures to maintain a unitarily assembledoil ring but is also chosen so that it has the characteristic ofbreakdown under higher than room temperatures to permit normal operationof the oil ring when assembled in an internal combustion engine. v

This invention relates to oil rings for use in conjunction with a pistonand in particular to unitized multi-component oil rings.

Piston oil rings which are disposed in a groove in a piston andsealingly engage the wall of the cylinder receiving the piston are oftenof the multi-component assembled type. These components include aplurality of cylinder wall engaging rails and means for axiallyseparating the rails and for applying a radially outward cylinder wallengaging bias to the rails; such means often being formed as a combinedspacer-expander.

Obviously, the fewest number of separate components, such as for examplea one-piece oil ring, would be more convenient in terms of storage,handling, and installation, if such can be constiucted in a manner so asto retain the desired function and operation. In the case ofmulti-component oil rings wherein the components are not unitized, thevarious components must be handled separately in installation and allthe components assembled in their proper relationship. A deleteriouscondition often occurring in assembling such separate components is thatthe ends of the combined spacer-expander will become overlapped andcannot function properly and also -improperly position the rails.Further, during the handling of the Various separate components, thesame tend to become entwined and tangled which wastes time in separatingthe same and often damages the components. Many other conveniences arealso realized.

The problem encountered in unitizing multi-component oil rings involvesutilizing means capable of holding the components in their assembledrelationship, which means will terminate the unitized relationship afterthe oil ring has been properly installed and thereafter not interferewith the functioning of the components. This requirement is particularlydemanding in oil rings which utilize a cornbined circumferentiallyexpansible spacer-expander, because in such an oil ring the rails tendto expand and contract radially while the spacer-expander tends toexpand and contract circumferentially. Hence, when installing the oilrings on a piston, which involves increasing the diameter of the oilring to position the same in the piston groove and then decreasing theoil rings diameter as the piston is installed in the cylinder, thespacerexpander tends to move circumferentially relative to the railswhich are expanding or contracting radially. This invention contemplatesutilizing strong, resilient adhesive means capable of holding the ringcomponents together during assembly yet still being capable of allowingdisassociation of the ring components upon initial engine operation.

It is, therefore, an object of this invention to provide 3,356,375Patented Dec. 5, 1967 ICC multi-component oil control rings wherein atleast some of the components thereof are unitized.

It is another object of this invention to unitize multiple component oilcontrol rings which include both radially and circumferentiallycompressible components.

It is still another object of this invention to unitize multi-componentoil control rings with an adhesive which loses its adhesive propertiesunder engine operating conditions.

It is still a further object of this invention to unit-izemulti-component oil control rings with an adhesive having strength whichis high at room temperatures but which decreases with increasingtemperature.

Another object of this invention is to provide means for preventing theends of the spacer-expander member of a multi-component oil ring frombecoming overlapped when assembled in a piston groove.

it has been found that various resins, when blended with properelastomers, plasticizers and fillers, form adhesives which are capableof holding a multi-component oil ring together prior to, during, andafter installation thereof on a piston. These adhesives must also changetheir characteristics under eng-ine operating conditions so as torelease the unitized components and may use a base resin selected, forexample, from epoxy resins, phenol resins, or polyvinyl-butyral resins,or a combination of these. Resins from these groups have been utilizedfor the purpose of this invention, but it is apparent that other typesof resins would serve the same purpose equally well. The importantfeature is that the properties for the specific use may be achievedthrough selection and variations in the base resins, elastomers,plasticizers, and/ or fillers.

Referring now to the drawings:

FIG. 1 is a plan view of a unitized oil control ring assembly in thefree state with a portion of the top rail cut away;

FIG. 2 discloses a portion of the assembly shown in FIG. 1 when viewedin the direction of the arrows 2 2 shown in FIG. 1;

FIG. 3 is a perspective view of a section of an oil control ring showingthe gap in the rails and with portions of the top rail cut away and theadhesive omitted for added clarity;

FIG. 4 is a view of the structure shown in FIG. 3 after the oil controlring has been unitized with adhesive;

FIG. 5 is a cross-sectional view of an oil control ring assemblypositioned in a piston groove and engaging a cylinder wall;

FIG. 6 is a view taken in the same manner as FIG. 2 of an oil ringhaving an offset gap and shown with its ends in an axially displacedrelationship and with the adhesive omitted for added clarity;

FIG. 7 is a vieW of the structure shown in FIG. 6 with the componentsunitized with adhesive; and

FIG. 8 is a view taken in the same manner as FIG. 2 of an oil controlring which has been unitized with the ends of the spacer-expander inregistration with the ends of the rails.

Referring now to the drawings, a piston oil ring assembly 10 comprises apair of annular rails 12 and 14 and a combined or unitarycircumferentially expansible and compressible spacer-expander 16 and isadapted to be installed within a peripheral annular groove 18 formed ina piston 20 and confined within a cylinder 22 of an internal combustionengine. The spacer-expander 16 is disposed axially intermediate therails 12 and 14 and is axially spaced from the piston 20 thereby. Apassage 24 .is formed in the piston 20 leading from the bottom of thegroove 18 to the interior of the piston for draining oil from thegroove.

Each of the rails 12 and 14 is preferably made from a fiat strip ofmetal, such as spring steel, and is provided with a radially extendinggap 13 to permit it to expand and contract in a radial direction whilethe circumferential length thereof remains substantially constant. Itshould be noted that in the assembled condition of the piston ringassembly 10, when the same is disposed in the groove 18 of the piston 20and confined within the cylinder 22, the ends 25 and 27 of each of therails 12 and 14, which border the gap 13 therein, still remaincircumferentially spaced from each other so as to permit the radialmovement of the rail. Accordingly, each rail is resilient and, byitself, exerts some outward pressure against the wall of the cylinder22. Further, it should be noted that in order to assemble the rails 12and 14 within the groove 18 it is necessary to radially expand the same.Additionally, when the piston is confined within the cylinder 22, thelatter Will radially compress the rails 12 and 14.

The spacer-expander 16 comprises a plurality of circumferentially spacedsupport members 26 connected by U-shaped spring members 28. The radiallyinner ends of the arms 29 of each spring member 28 are integrallyconnected to adjacent support mem-bers 26 and extend radially outwardlytherefrom. A11 opening 3f) is formed at substantially the center of eachsupport member 26 for oil drainage purposes, and the arms 29 of thespring member are axially reduced in thickness to provide passagewaysbetween the same and the rails 12 and 14 for oil drainage purposes. Atab 32 is formed on each of the lower and upper sides of each supportmember 26 and extends axially outwardly and radially inwardly therefromto a position wherein the same engage the radially inner edge 33 of eachof the rails 12 and 14. Each U-shaped spring member 28 is formed with apair of axially and oppositely extending engaging portions 34 formed atits radially outer extremities which portions 34 axially engage theinner surface 44 of the rails 12 and 14 adjacent the outer peripherythereof and hold the same in an axially spaced relationship.

While the spacer-expander 16 is of substantially annular configuration,the same is of greater circumferential length than the rails 12 and 14and is formed with a pair of juxtaposed circumferential ends in the formof radially extending plates 36 and 3S which plates preferably have anaxial dimension which is equal to the desired axial space between therails 12 and 14 and are adapted to be in abutting engagement when thespacer-expander is operatively confined within the cylinder 22 while theends 25 and 27 of t-he rails 12 and 14 remain spaced.

The spacer-expander 16 is made from resilient sheet metal, and iscircumferentially compressible and expansible, and, when the same isoperatively confined within the cylinder 22 with the plates 36 and 3S inengagement, it is circumferentially compressed and tends to expand andthereby increase its circumferential dimension. Such increase incircumferential dimension is accompanied by an increase in diameter andcauses the spacer-expander 16 to exert a radially outward pressureagainst the inner peripheries 33 of the rails 12 and 14, thereby forcingthe latter against the cylinder wall 22 with an urging force which addsto the urging force supplied by the resilient qualities of the rails 12and 14 themselves.

In the preferred embodiment of this invention two different adhesivesare used to unitize the components of the oil ring 10 prior to theassembly of the latter in the groove 18 of the piston 20. A first, orprimary, adhesive 40 secures the spacer-expander 16 in the vicinity ofthe ends and 27 of the rails 12 and 14 so that the ends 36 and 38 of thespacer-expander are juxtaposed. It should be noted that to place thespacer-expander 16 within the rails 12 and 14 with its ends 36 and 38juxtaposed, the spacer-expander must be circumferentially compressed andits circumferential length decreased. Since the spacerexpander 16 iscircumferentially compressed, the same is attempting tocircumferentially expand and, in so doing, the tabs 32, which are inengagement with the inner periphery 33 of the rails 12 and 14, tend tourge the rails axially apart and radially outwardly. Since the rails 12and 14 at this time are not contained within the piston groove 18, wherethey would be restrained from moving axially apart, the rails wouldseparate axially and allow the spacer-expander to pop out therebetweenand circumferentially expand.

To prevent such axial separation of the rails 12 and 14, a second orsecondary adhesive 42 secures the inner periphery 33 and the innersurface 44 of the rails to the tabs 32 and projections 34, respectively,of the spacer-expander, thereby preventing the rails from separatingaxially and the spacer-expander from popping out ybeyond the rails.

Both the primary adhesive 40 and the secondary adhesive 42 arestructural adhesives which are characterized as having an adhesivestrength which is sufficiently high and stable at room temperature tounitize the components but decreases rapidly with elevated temperatures.

As shown in FIG. 3, a void 46 is provided by the components of the ringassembly 10, which void is partially bounded by the opposed surfaces 44of the rails adjoining the ends 25 and 27 thereof and the plates 36 or38, the adjacent arm 29 and the support member 26 connecting the plateand arms of the spacer-expander 16. As shown in FIG. 4, the Void 46 isfilled with primary adhesive 40, thereby adhesively bonding the portionsof the spacerexpander and the rails surrounding the voids 46. Preferablythe adhesive 40 is relatively thick so that it will remain in the voidand not run or disperse itself to undesired locations. It is preferredthat the ends 25 and 27 of the rails 12 and 14 be axially aligned asshown in FIGS. 1-4, although, as shown in FIG. 6 and hereinafterdescribed, one rail 12A may be rotated circumferentially relative to theother rail 14 thereby providing an offset gap between the ends of therails.

Since the bonding with the secondary adhesive 42 is only -by the tabs 32and the projections 34 to the rails 12 and 14, adhesive need only beapplied at these locations; however, the secondary adhesive 42, forconvenience, is preferably applied as a thin coating to the entire innerperiphery 33 and inner surface 44 of the rails 12 and 14 prior to theassembly of the components of the ring 10 so that the portions 32 and 34of the spacer-expander 16 are bonded to the rails. The thin layer ofadhesive 42 on the rails 12 and 14 at the locations removed from theportions 32 and 34 do not interfere with normal operation of theassembly.

In an alternative means for bonding the ring assembly, the primaryadhesive 40 may be applied in the voids indicated at 47 which voids areintermediate the first and second successive engaging portions 34following plates 36 and 38 and are bounded by the opposed surfaces 44 ofthe rails 12 and 14, a pair of adjacent arms 29 and a supporting member26 of the spacer-expander 16. The secondary adhesive is applied to theinner peripheries 33 and surfaces 44 as described previously. Theadvantage of this alternative method is that more surface area of therails 12 and 14 and of the spacer-expander 16 is exposed for contactwith the adhesive 40, thereby resulting in a stronger bond between therails and spacer-expander for compression of the latter while stillsecuring the ends 36 and 38 of the spacer-expander to the ends 25 and 27of the rails.

The unitized oil ring in FIG. 6 is shown with its ends in an axiallydisplaced relationship so that the construction of this assembly may beclearly demonstrated, In this embodiment, during assembly of the ringcomponents, one of the rails, for example the top rail 12A, iscircumferentially rotated relative to both the bottom rail 14 and thespacer-expander 16 so that its end 27A is disposed adjacent the engagingportion 34A and its end 25A extends to the tab 32A. That is, the toprail 12A is rotated approximately the distance indicated at 52.

The primary adhesive 40A is applied within a void indicated at 46A,which void is partially bounded by the rails 12A and 14, the plate 36and the arms 29A to adhesively bond the spacer-expander 16 to the end 25of the rail l14 and to the inner surface 44 of the rail 12A bounding thevoid 46A. Primary adhesive 40B is applied within the void indicated at47A, which void is bounded by the rails 12A and 14, the portions 34A and34B, the support 26A, and the arms 29C and 29D, to bond thespacerexpander 16 to the end 27A of the top rail 12A and to theadjoining inner surface 44 of the rail 14. The void 46B adjacent theplate 38 should not be filled with primary `adhesive 40B since the innerend 25A of the rail 12A should not be 'bonded to the spacer-expander 16at this location, -otherwise the adhesive Would interfere with thecircumferential movement of the top rail 12A.

The secondary adhesive is applied to the entire inner periphery 33 andinner surface 44 of the rails 12A and 14 except for that portion of theinner surface -of the top rail 12A indicated at 48 which extends beyondthe plate 36 and overlies .the plate 38 of the spacer-expander 16. Withthis method of assembly, a unitized oil ring is provided having anoff-set gap 50 which is still capable of expansion for installation on apiston and subsequent compression for assem-bly into the cylinder 22.Since the plates 36 and 38 of the spacer-expander 16 are secured to therails 12 and 14 there is no opportunity for the same to becomeoverlapped during the assembly operation so that the spacer-expander ismaintained in a spaced relationship relative to the piston 20 with itsplates 36 and 38 juxtaposed.

An extension of this alternative method of assembly to obtain an off-setgap would be to rotate the top rail 12A relative to the spacer-expander-16 the distance 52, as shown in FIG. 6, and also to counterrotate thebottom rail 14 this same distance and utilizing suitable cementingprocedures to obtain the expansion capability of the unitized ring.

Still another method of assembly, as shown in FIG. 8, is by placing thegap 13 of the ends 25 and 27 of the rails 12 and 14 in axial alignmentwith one another and bonding the spacer-expander 16 to the rails in amanner that the ends 36 and 38 of the spacer-expander are inregistration with the ends and 27 0f the rails respectively.

The preferred composition of the primary adhesive 40 is as follows:

Ingredients: Weight percent Epon 828 69.0 Thiokol LP-3 17.3 DMP- 7.2Cab-O-Sil, Type M-S 6.5

(Total solids 100%) 100.0

Epon 828, a product `of Shell Chemical Company, is a liquid bisphenolA/epichlorohydrin type epoxy resin having an epoxide equivalent weightof 18S-200.

Thiokol LP-3 is a low molecular weight liquid polysolfide polymercomposed of repeating formal groups which are linked by sulfur to sulfurbonds and terminated by mercaptan groups. Additional mercaptan groupsoccur at intervals on the chain of repeating formal groups which providecross linkages at various points. This polymer is a product of ThiokolChemical Corporation.

When in the presence of a suitable activator or curing agent, epoxyresins co-react by an additional reaction with the Thiokol LP-3polysuliide polymer, thereby forming longer chain polymers. Aliphatic oraromatic amines are the most common activators and approximately tenparts of amine activator, or curing agent, per one hundred parts epoxyresin is required. 'I'he relative amount of the polysulde polymerblended with the epoxy resins governs the ultimate properties of thecured adhesives, such as shear strength and temperature stability.

The aromatic amine activator, or curing agent, used in the polysulideepoxy ladhesive formulation is DMP-30,

6 a product of Rohm and Haas Chemical Company. Its chemical name istridimethylamino methyl phenol.

The Cab-O-Sil, Type M-5, is a product of Godfrey L. Cabot, Inc. and isdefined as an ultrafine pyrogenic silica, sometimes referred to ascolloidal silica because of its tine particle size range of 0.015-0020micron. The Cab-O-Sil is employed in the liquid adhesive formulation asa thickening or bodying agent, and to provide adequate thixotropy. Thethixotropic properties imparted to the adhesive by the addition of finesilica aids in preventing any running or sagging of the adhesive duringthe heat-cure cycle.

The Epon 828, Thiokol LP-S and Cab-O-Sil Type M-5 were accuratelyweighed into a suitable container and mixed by hand to wet-out theCab-O-Sil. This mixture was then given three passes over a 3-rolllaboratory size paint mill to insure uniform dispersion of theCab-O-Sil. Following the milling step, the appropriate amount of DMP-30(curing agent) was stirred into the base adhesive. At this point theadhesive was ready for use and had an effective pot-life of about 20minutes.

This primary adhesive 40 may be cured by heating the same in air -up toa temperature of 300 F. for thirty minutes. After curing and cooling,the adhesive 40 is stable, that is, it has sufiicient Strength tomaintain the spacer-expander 16 bonded in its compressed state to therails 12 and 14, up to a temperature of 140 F. and will lose sufficientof its adhesive properties substantially immediately when exposed tomotor oil at approximately 180 F., the operating temperature of theconvention internal combustion engine, so that the forces imposed on theadhesive 40 by the `compressed spacer-expander 16 will easily disruptthe bond afforded thereby and the spacer-expander is released from therails 12 and 14 to expand and contract circumferentially.

The primary adhesive 40 may be used to spot bond the entirecircumference of the ring assembly, but it is preferable to use thisadhesive at the ends of the rails only and to use the secondary adhesive42 for bonding other portions of the spacer-expander to the rails toovercome pop-out, which adhesive is preferably in a fluid solution stateso that it may be spread as a relatively thin coating. Pop-out of thespacer-expander would occur due to the fact that there is nothing tomaintain the axial distance between the rails prior to installing thering 10 in the piston groove 18 and the tabs 32 attempt to urge therails axially apart. When installed, the ring assembly is placed in agroove 18 of the piston 20 which groove, together with thespacer-expander 16 keeps the rails 12 and 14 in position. Obviously,prior to installation Within the groove 18, the spacer-expander 16 wouldhave a tendency to slip radially outwardly and past the two rails 12 and14 in a pop-out position thereby relieving the desired circumferentialcompression therein and in such pop-out position, the assembly cannot beplaced in the groove 18.

The preferred secondary adhesive is based on a polyvinylbutyral-phenolic resin blend. The adhesive found to provide satisfactoryresults in this application has the following composition:

Ingredients: Weight percent Burvar B-76 14.0 Durez 12687 7.0 Toluene55.0 Alcohol l# 30 24.0

(Total solids 21%) 100.0

Burvar B-76 is a polyvinyl butyral resin produced by Shawinigan ResinsCorporation and may be characterized as being 88% butyral, 0-2.5%acetate, and 9.0-13% hydroxyl. Durez 12687 is a thermosetting phenolicresin which may be obtained from Durez Plastics Division of HookerElectrochemical Company.

Combinations of polyvinyl butyral resin with phenolic resins arecommonly used in the manufacture of structural adhesives. The polyvinylbutyral-phenolic adhesive gives very high shear strength values at roomtemperatures, but its shear strength decreases rapidly with increasingtemperatures.

The secondary adhesive is a fluid solution and may be applied in thedesired thin coating by brush to various points around the ringassembly. Following evaporation 0f the solvent at room temperature, thepieces are assembled and the adhesive is activated and heat cured. Aftercuring and cooling the secondary adhesive 42 is also stable, that is, ithas sufficient strength to maintain the spacer-expander 16 bonded in itscompressed state to the rails 12 and 14, up to a temperature of 140 F.,and will lose sufficient of its adhesive properties substantiallyimmediately when exposed to motor oil at approximately 180 F., theoperating temperature of the conventional internal combustion engine, sothat the forces imposed thereon by the compressed spacer-expander 16will easily disrupt the bond afforded thereby, and the spacer-expanderis released from the rails 12 and 14 and may move circumferentiallyrelative to the rails. Actually, the secondary adhesive 42 is notnecessary after the ring 10 has been assembled in the piston groove 18,since the groove will then prevent axial separation of the rails 12 and14.

This secondary adhesive 42 is prepared by mixing appropriate amounts oftoluene and alcohol and dissolving the resins therein by mechanicalstirring. This adhesive solution is then brushed onto the cleanedopposed surfaces 44 of the rails and the projectors 34 of thespacerexpander; the primary adhesive 40 is applied to the ends of therails 12 and 14 and in the voids 46 of the spacerexpander 16 and thering assembly is placed in a holder which keeps the components of theassembly compressed in the relationship shown iii FIGS. 4 or 7. The ring10 is then kept at room conditions until the solvents of the secondaryadhesive 33 evaporate. The ring assembly in the holder is then heated at300 F. for 30 minutes to com plete the curing of the adhesives.

in comparing the two adhesives used in this invention, the primaryadhesive has higher viscosity than the secondary adhesive and for thisreason is applied in sufiicient quantity to the ends of the rails tohold the components in place. This primary adhesive is applied heavilyand completely fills the voids 46, 47 or 47A. Because the primaryadhesive is considerably more viscous than the secondary adhesive, itcannot conveniently be applied in small quantities within the innersurfaces 44 of the rails 1?. and 14. Since it is desirable to limit theamount of adhesive placed on the inner surfaces 44 so that the openingsbetween the arms 29 of the spacer-expander 16 and the rails 12 and 14a-re not filled, thereby preventing oil ventilation, the primaryadhesive is not as suitable in this location as the secondary adhesive42 which, due to its lower viscosity, can be applied in a thin film tothe inner surfaces 44 of the rails 12 and 14. The secondary adhesive 42has sufficient viscosity to adhere to the inner peripheries '33 andsurfaces 44 when applied thereto in sufiicieiit `quantity and -toprevent pop-out of the spacerexpander.

The secondary adhesive 42 while being stable up to a temperature of 140F. loses its shear strength more rapidly with increasing temperature andreleases the ring components sooner than the -primary adhesive 40 sothat it will also lose its adhesive properties upon initial exposure toconventional internal combustion engine opera-ting conditions.

The secondary adhesive 42 alone maybe used to unitize the ring assemblyhowever, because of the low viscosity of this adhesive, it is preferableto place a filling material either in voids 46 or voids 47 which wouldserve as a lbase for the adhesive. Such a filler may be made fromplastic, wood, metal or the like. This filler would be a -permanent partof the ring assembly, but would not interfere with the operation of theother components.

Although the preferred embodiment of this invention has been shown anddescribed, changes and modifications can be made. The precedingdescription is illustrative only and not for the purpose of renderingthis invention limited to the details illustrated or described exceptinsofar as they have been limited by the terms of the following claims.

What is claimed is:

1. A multi-component oil ring assembly adapted for insertion in a pistongroove comprising in combination a pai-r of circumferentially extendingaxially spaced rail means, a circumferentially extending andcircumferentialiy resiliently precompressed spacer-expander meansengaging and urging said rail means radially outwardly and having atleast a portion thereof disposed intermediate to and axially spacingsaid rail means, and a resinous adhesive means acting in shear to bondsaid precompressed spacer-expander means to said rail means, saidadhesive means having a shear strength which is sufficiently high to`bond said spacer-expander means to said rail means at room temperaturesand maintain the compression thereof and which shear strength atapproximately 1807 F. is insuflcient to maintain the compression of saidspacer-expander means whereby said adhesive means releases saidspacer-expander means from said rail means when exposed to internalcombustion engine operating conditions.

2. An oil ring as described in claim 1 wherein at least a portion ofsaid resinous adhesive means comprises 80% epoxy resin, 10-25%polysulfide polymer, 5-10% thixotropic agent, and 5-l0% curing agent.

3. An oil ring as described in claim 2 wherein said epoxy lresin isbisphenol A/epichlorohydrin, said liquid polysulfide polymer has a lowmolecular weight, said trixotropic agent is pyrogeiiic silica and saidcuring agent 1s an aromatic amine activator.

4. An oil ring as described in claim 1 wherein at least a portion ofsaid resinous adhesive comprises 10-20% polyvinyl butyral resin, 5-l0%phenolic resin, 50-60% aromatic amine activator and 10-30% alcohol.

5. An oil ring as described in claim 4 wherein said phenolic resin isthermosetting, and said aromatic amine activator is toluene.

l6. A multiple component oil ring comprising a pair of coaxial,circumferentially extending and axially spaced rails having opposedinner surfaces and each having a radially extending gap, a unitarycircumferentially extending spacer-expander having a first portionthereof disposed axially intermediate and coaxial with said rails forspacing the same and a second portion thereof engaging said rails forurging the saine radially outward and circumferentially opposed endportions adapted to circumferentially engage each other, and adhesivemeans bonding said end portions of said spacer-expander to at least oneof said rails in axial alignment with the gap therein for maintainingsaid end portions in a circumferentially spaced relationship and bondingsaid first portions of said spacerexpander to the inner surface of atleast said one rail for maintaining said spacer-expander coaxial withsaid rails.

7. A multi-component oil ring for mounting in a groove of'a pistoncomprising a pair of coaxial, axially spaced rails having opposed innersurfaces and each having a pair of circumferentially opposed endportions defining a radially extending gap therebetween, a unitaryspacerexpander having a rst portion thereof disposed axiallyintermediate said rails for spacing the same and a second portionthereof engaging said rails for urging the same radially outwardly andcircumferentially opposed and adjacent end portions adapted tocircumferentially engage each other, a first resinous adhesive bondingsaid end portions of said spacer-expander to said rails on opposedcircumferential sides of the gap therein and a second resinous adhesiveapplied to the inner surfaces of said rails and securing t-he same tosaid fir-st portions of said spacer expander to contain saidspacer-expander intermediate said rails.

8. An oil ring as described in claim 7 wherein said spacer-expander isof greater circumferential length than said rails and has juxtaposedends in axial alignment with said radially extending gaps of said rails.

9. An oil ring as described in claim 7 wherein each of the opposed endportions of one of said rails is in axial alignment with one of saidopposed end portions respectively of the other of said rails, one ofsaid end portions of said spacer-expander is in axial alignment witheach of the aligned ends respectively of said rails, and said firstadhesive bonds said aligned end portions to each other.

10. A multi-component oil ring assembly for insertion in a piston ringgroove comprising a pair of circumferentially extending, axially spacedcylinder engaging rails, each of said rails having an inner surface anda radial width greater than its axial thickness and having a pair ofcircumferentially opposed and spaced end portions forming a radiallyextending gap therebetween, a circumferentially extendingspacer-expander for axially spacing and radially outwardly urging saidrails and comprising a plurality of adjacent circumferentially spacedand circumferentially compresslble and expansible resilient membersdisposed intermediate said rails, connecting members interconnecting theadjacent of said resilient members, tab means formed on at least some ofsaid mem-bers and engaging the radially inner edges of said railswhereby said spacer-expander is operative to urge said rails radiallyoutwardly, axially opposed engaging means formed on at least some of themembers of said spacer-expander and engaging the axially inner surfaceof and axially spacing said rails, said spacer-expander having a pair ofcircumferentially opposed end portions in axial alignment with said gapbetween the opposed end portions of one of said rails, a -rst adhesivebeing adhesively stable at room temperatures and being operative to loseits adhesive properties under internal combustion engine operatingconditions and being applied axially intermediate said rails and bondingthe aligned end portions of said spacer-expander to at least said onerail, and a second adhesive means being adhesively stable at roomtemperature and operative to lose its adhesive properties under internalcombustion engine operating conditions and being applied to the innersurface of said one rail and bonding the same to at least some of saidengaging means engaging the same whereby said iirst and second adhesivemeans 4unitize said one rail and said spacer-expander.

11. The oil ring of claim 10 wherein said spacer-expander has acircumferential length substantially -greater than the circumferentiallength of said one rail, said spacer-expander is circumferentiallycompressed so that its circumferential length is only slightly greaterthan said one rail and its end portions are in axial alignment with saidgap between the opposed end portions of Said one rail, and said rstadhesive bonds said spacer-expander at said opposed end portions to eachof the ends of said one rail and retains said spacer-expander in itscircumferentially compressed condition.

12. A multi-component oil ring assembly adapted for insertion in apiston ring groove comprising in combination a pair of axially space-d,circumferentially extending rail means, circumferentially extending andcircumferentially compressible and expansible spacer-expander meanshaving a greater free circumferential length than said rail means, saidspacer-expander means being circumferentially precompressed to acircumferential length slightly greater than said rail means and rbeingdisposed coaxially with and axially intermediate said rail means foraxially spacing and radially outwardly urging the latter, and meansacting in shear for releasably unitizing said circumferentiallycompressed spacer-expander means to said rail means, said means forreleasably unitizin-g said circumferentially compressed spacer-expandermeans comprising a resinous adhesive means having stable bondingproperties at room temperatures and being operative to lose its bondingproperties When exposed to external combustion engine conditions, saidadhesive means bonding said spacer-expander means to said rail means.

13. A multi-component oil ring adapted for insertion in a piston ringgroove comprising in combination a pair of coaxial circumferentiallyextending and axially spaced rails each having a pair ofcircumferentially opposed and spaced end portions dening a radiallyextending gap therebetween, a unitary spacer-expander having a tirstportion thereof disposed axially intermediate said rails for spacing thesame and a second portion thereof engaging said rails for urging thesame radially outwardly and circumferentially opposed and adjacent endportions adapted to circuinferentially engage each other, saidspacer-expander being circumferentially longer than said rails when theend portions thereof are in engagement and being circumferentiallyprecompressed to a circumferential length greater than thecircumferential length of one of said rails but less than the sum of thecircumferential length of one of said rails and the circumferentialdistance between the opposed end portions thereof and with the endportions of the spacer-expander circumferentially spaced, and adhesivemeans bonding said circumferentially cornpressed spacer-expander to saidrails, each of said opposed end portions of one of said rails is inaxial alignment with one of said opposed end portions respectively ofthe other of said rails, said end portions of said spacer-expander'arein axial alignment with the gaps of said rails and said adhesive meanscomprises a first and second resinous adhesive means, said lirstadhesive means bonding said end portions of said rails to saidspacer-expander and said second adhesive means bonding said lirstportion of said spacer-expander to said rails.

References Cited UNITED STATES PATENTS 2,140,710 12/1938 Meisel 277-1 X2,293,450 8/ 1942 Wilkening 267-15 2,781,899 2/ 1957 Schmank 206-462,854,301 9/1958 Lutz 267-1.5 3,004,811 10/1961 Mayfield 277-141 X3,099,560 7/ 1963 Kouri 96-78 3,140,096 7/ 1964 Rodenkirchen 277-141LAVERNE D. GEIGER, Primary Examiner. J. S. MEDNICK, Assistant Examiner.

1. A MULTI-COMPONENT OIL RING ASSEMBLY ADAPTED FOR INSERTION IN A PISTONGROOVE COMPRISING IN COMBINATION A PAIR OF CIRCUMFERENTIALLY EXTENDINGAXIALLY SPACED RAIL MEANS, A CIRCUMFERENTIALLY EXTENDING ANDCIRCUMFERENTIALLY RESILIENTLY PRECOMPRESSED SPACER-EXPANDER MEANSENGAGING AND URGING SAID RAIL MEANS RADIALLY OUTWARDLY AND HAVING ATLEAST A PORTION THEREOF DISPOSED INTERMEDIATE TO AND AXIALLY SPACINGSAID RAIL MEANS, AND A RESIONOUS ADHESIVE MEANS ACTING IN SHEAR TO BONDSAID PRECOMPRESSED SPACER-EXPANDER MEANS TO SAID RAIL MEANS, SAIDADHESIVE MEANS HAVING A SHEAR STRENGTH WHICH IS SUFFICIENTLY HIGH TOBOND SAID SPACER-EXPANDER MEANS TO SAID RAIL MEANS AT ROOM TEMPERATURESAND MAINTAIN THE COMPRESSION THEREOF AND WHICH SHEAR STRENGTH ATAPPROXIMATELY 180* F. IS IN SUFFICIENT TO MAINTAIN THE COMPRESSION OFSAID SPACER-EXPANDER MEANS WHEREBY SAID ADHESIVE MEANS RELEASES SAIDSPACER-EXPANDER MEANS FROM SAID RAIL MEANS WHEN EXPOSED TO INTERNALCOMBUSTION ENGINE OPERATION CONDITIONS.